TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

[Scuse]

I have a 50" Panasonic Plasma TV model: TC-P50G20 that I need help diagnosing a problem on. It worked great till one day recently I heard a pop and it cut off. I tried unplugging it for a few hours then plugged it back in and didn't work. I tried this several times and only got the protection mode with four flashes. After getting a service manual online I saw this was a power board problem so i ordered a used one on ebay. After installing this board i started getting two different results depending on how fast I turned the TV on after plugging it in. If I hit the power button immediately I got the same four blinks, but if I let it sit for a few minutes then hit the power button I got ten blinks which says it could be the a-board, sc-board, ss-board, or p-board. The caps seemed to be raised a bit when I received the board so I was concerned before even putting it in but tried it anyways. After this result I returned it immediately and purchased another power board (used) from a different company. Now that I have put this board in, with similar looking slightly raised caps, I don't get any flashes or blinks but also no picture or sound. The power board just continues to click in about one second intervals from what I think is a relay. I've read that this may be a problem with the caps, but don't want to change them and void the warranty and not be able to return the board. I'm probably going to send this one back as well and try once again to buy from another dealer. I would really appreciate any help or comments I could get at this point. I've heard that it may also be a sustain or main board problem. Thanks in advance!

[tom66]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

The caps are fine. It is a Panasonic, they use good caps.
You probably have an SC board failure. tw2005 has successfully fixed some of the G10 models, I think -- the boards should be quite similar for the G20.

[Scuse]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

Thanks for your reply. I may try ordering an sc-board as you recommended. Before I do is the anything I can test to verify this is the problem? Also which power board should I use? I have gotten different voltage reading across each one I've had and the original certainly had two bad fuses at least. Do you think the most recent one I purchased would work even if the "relay" is clicking continuously and I'm not getting a standby error code?

[tom66]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

You should put your original board in. Check blinks. 4 blinks: P, SC, SS, A.

Unplug the SC board. If you get 6 or 7 blinks, the SC/SU/SD is at fault. Then, re-connect SC board.
Unplug the SS board. If you get 8 blinks, the SS is at fault.

The SU/SD and SC should be replaced at the same time.

[Scuse]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

I'm working on that right now but isn't the 4 blinks just the p board and the 10 blinks the code for the 4 different boards?

[tom66]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

2, 4 and 10 blinks are P board. Basically you are looking for a change from the current code, not 4 blinks. My error.

[Scuse]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

Okay just finished. I put the original board in, and unplugged the SC Board. I plugged it in, turned it on, and got seven blinks which is certainly a change. I plugged the SC board back in and in plugged the SS board while the TV was unplugged. I then plugged the TV back in and got four blinks again.

[tom66]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

SC is failed, then. Common fault... Best to see if tw2005 chimes in as he knows exactly what to replace.

[Scuse]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

It seems that by what you said the sc, su, or sd boards are bad. I don't have a clue but seems logical that you would get a different reading if a working part were disconnected and get an unchanged reading if you disconnected a part that was bad in the first place. I take your advice as that of an expert but just my way of thinking

[tom66]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

In this case, the way the parts fail on this model is dead short. So you are removing the short by disconnecting the board which changes the fault code from 4 blinks (P Board SOS overload, 15V detect, etc.) to 6 blinks/7 blinks (SC floating voltage/chassis detect). The 7 blinks is a symptom of the TV jumping to the next "failure" after the 4 blink cause is removed. Note Panasonic have a lot of fault detection systems on their TVs. Samsung/LG plasmas will normally run without a board connected or with a fault detected but at the risk of causing more damage.

[Scuse]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

So if I replace the SC board there will still need to be another problem needing to be resolved? Is that likely to be the SU/SD boards? Would I need to change these as a set?

[tom66]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

It is recommended to replace SU/SD and repair SC. The SC is in short supply so replacements are very expensive.

[tw2005]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

Yep, so you have a failed SC board shorting vsus on the PSU, you've isolated the SC and had a change from SOS4 to SOS7 this clears the PSU.

So you need a replacement SC and you can test the SU/SD boards. If they test with no shorts or low resistances then I'd re-use them. On my TV i was lucky as they tested ok but I did replace them initially but have used my old ones since with no problem.

If you make a mistake and use shorted buffers they will blow the SC, that happened to me on my brother-in-laws TV as i assumed his TV failed in the same manner without checking. expensive mistake.

I could attempt to coach you on repairing these SC but this has the risk of me missing something and assumes they all fail in the same manner but I did repair 2 of 3 failed boards, still awaiting some additional parts in hope to complete that one.

I expect your SC is rev AF? AP & AW will work as well. With the AW it has an additional ceramic cap at C16461 (C461) 1000PF, 630V. I've left it in with no visual difference but could be removed and that then will be the same as the AF/AP.

As a guide for the buffer boards here's some results.

I found placing the red probe to the gnd plates and black to the pinouts gave the most accurate result for resistance.

Edit: The PSUs suffered no damage on both TVs I fixed, no fuses blown. I just read you mentioned fuses blown on the PSU.

[Scuse]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

Yes I have the rev. AF. Thanks for the input. I'm going to keep looking for an SC to buy for now. Ill definitely test the buffers for shorts using your numbers. If you use a jumper to test the SC50 connector to see if the problem is coming from the SC or SU/SD could this confirm that the SU/SD is good and only the SC is bad or would that just tell you if the SC is bad and the SU/SD could still be shorted? I haven't done this yet, and do intend to test the SU/SD as you instructed but am just curious and would like the extra piece of mind that I do/don't need the SU/SD boards. Thanks again

[tw2005]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

SC50 jump will only confirm whether SC is good or bad but with a SOS4 going to SOS7 with SC disconnected I would not bother. The SC is shorted which you could easily determine by measuring the input resistance at SC2 Vsus or probe some of the IGBTs for shorts. I'm sure it won't take you long to find a problem.

There's no other way but to probe the buffers , even if you purchase replacement buffers secondhand you must check them as you can't assume the seller has!

I've got 2 full sets here and 1 SC supplied as shorted. I managed to rebuild the SC and get it going.

Not impossible to rebuild but it's a calculated risk that you accept that you may get it wrong and it will take a while if you source the parts from china which is the cheapest way.

VSC_F should be VSCN_F in my table, I think anything above 190K is ok for that, I think I may have received a board with that one shorted too but It should be obvious if you do find one bad.

[Scuse]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

i went ahead and ordered a new(used) sc, and got lucky enough to find one with su/sd boards that come with it. I just put in the new sc board and wanted to check to see if it was good so I checked the sc50 jumper with the su/sd boards disconnected. I didn't have any spare wire so I just ran a screw in there to connect the two wires. I know...I know..but anyways it fired up. I had a really blotchy blue picture that only covered part of the screen but it lit up. I'm gonna check the new su/sd boards as well as my old ones before trying to put it all together. Any advice before I take the leap? Is that normal for the picture to look that terrible with it just jumpered by a screw? Thanks for your help!

[tom66]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

Did you have SU/SD connected with the SC50 jumper?
If the picture was visible, but very poor, you probably need to adjust the board to the specification in the service manual.

[Scuse]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

su/sd were not connected with jumper in place and tv on. I tested my original su/sd and they seem to be okay. one of the "used working" boards i received tested bad before installing so i'm putting my originals on the tv now.

[tom66]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

It's unusual that you would get any light without SU/SD, but this is a NeoPDP... new technology. Try with boards installed, you may need to adjust SC pots if picture is poor.

[Scuse]

Re: TC-P50G20 Panasonic 50" Plasma 4 blinks / 10 blinks

sc pots? It came on with the su/sd plugged in, but just barely lit up. cant get any screen even menu to come up. I still have the back off if this may affect anything, and when it turns on the led isn't blinking at all but is solid red